Conventionally, multi-joint robots are made up of a plurality of rotation axes. This makes it significantly difficult for an operator to manually operate a multi-joint robot using a teaching box. Even if the operator is proficient in the operation, when some interfering substance exists around the multi-joint robot, the interfering substance might interfere with the multi-joint robot due to, if any, incorrect axis selection or an incorrect moving direction. In view of this, the operator gradually moves the multi-joint robot carefully, taking the optimal axis selection and the optimal moving direction into consideration. Thus, operating multi-joint robots is a significantly nerve-wracking kind of work for operators and a laborious kind of work. In view of this, in Japan, to be qualified to operate a multi-joint robot, one is required to attend a course prescribed by law and be granted a license.
General operators who lack experience of robot operation are unable to operate systematized multi-joint robots as accessories of NC machine tools. Thus, machine tools of this kind have not been widely employed except in some special cases where use of a multi-joint robot is inevitable.
Patent document 1 discloses an industrial robot provided with a plurality of switches corresponding to a plurality of respective operation programs. When a switch is pressed, the corresponding program is read, and the industrial robot executes the program. Patent document 2 discloses that operating an activation switch on a teaching pendant for a long period of time activates a robot in continuous operation mode, while operating the activation switch for a short period of time activates the robot in single block driving. Both patent documents give no consideration to operators who are not used to robot operation in systemized NC machine tools using multi-joint robots.